1. Field of Technology
The present disclosure relates to clad alloy substrates and to methods of making such clad materials. The present disclosure also relates to articles of manufacture made from or including clad alloy substrates and to methods of making such articles of manufacture.
2. Description of the Background of the Technology
In certain applications requiring a material combining high strength with corrosion resistance, clad alloys are used. One common example of a clad alloy exhibiting favorable strength and corrosion resistance includes a stainless steel layer clad on its opposed surfaces with a layer of nickel or a nickel-base alloy (i.e., an alloy that is predominantly composed of nickel). Applications in which such clad materials are used include chemical cisterns, chimney flues, batteries, tubing, heat exchangers, piping for oil and gas, tanks for chemicals, and cookware. The stainless steel layer provides relatively high strength, while the nickel or nickel-base cladding layers resist corrosion under demanding conditions. Using a nickel dual-clad stainless steel of this type also has the advantage that the composite material is less expensive than certain high alloy content superaustenitic stainless steels and nickel-base alloys providing similar corrosion resistance properties.
The cladding process involves cladding a substrate material with either a single cladding layer or with a cladding layer on each of the substrate's opposed surfaces. The process used to produce a clad alloy must bond the one (single-clad) or two (dual-clad) cladding layers to the substrate sufficiently to prevent delamination of the cladding layers while under service conditions. Several cladding methods are known.
One known method for producing a clad stainless steel is described in U.S. Pat. No. 4,936,504. More specifically, the '504 patent describes methods for cladding stainless steel with various materials including copper, nickel and invar (an iron-36% nickel alloy). In general, the '504 patent describes a method wherein sheets of the stainless steel substrate and the cladding materials are stacked together and then rolled into a tight coil. The coil is heated in a vacuum furnace at high temperature for an extended period, thereby diffusion bonding the sheets of cladding materials to the stainless steel sheets. Significant energy is required to operate the vacuum furnace equipment and maintain the coil at elevated temperature for an extended period when conducting the '504 patent's method, and this adds substantially to the cost of the finished clad material.
U.S. Pat. No. 5,183,198, describes a method for producing a clad steel plate wherein a stainless steel or nickel alloy is clad onto an iron-base substrate comprising 0.020 to 0.06% carbon, 0.5% or less silicon, 1.0 to 1.8% manganese, 0.03% or less phosphorus, 0.005% or less sulfur, 0.08 to 0.15% niobium, 0.005 to 0.03% titanium, 0.05% or less aluminum and 0.002 to 0.006% nitrogen. (All percentages herein are weight percentages unless otherwise indicated). Slabs of the cladding material and the substrate material are rolled to plates of prescribed thickness. After smoothing, cleaning and degreasing all contact surfaces of the plates, an assembly slab is prepared by sandwiching a plate of the iron-base substrate material between two plates of the cladding material. The periphery of the assembled plates is then seal-welded and a vacuum pump used to remove air between the plate's contact surfaces. The assembly slab is then heated in the range of 1100° to 1250° F. and subjected to one or more rolling and cooling steps to adhere the materials and form the clad product. As such, in contrast to the method of the '504 patent, which utilizes a vacuum furnace, the '198 patent teaches creating a vacuum only in the space between the opposed surfaces of the cladding material and the substrate material.
In yet another known method for producing clad materials, known as explosion cladding, the controlled energy of a detonating explosive is used to create a metallurgical bond between two or more similar or dissimilar materials. Explosion cladding is a cold pressure process in which contaminant surface films on the materials to be bonded are plastically jetted off the base metals as a result of a high-pressure collision of the two metals. During the high velocity collision of metal plates, a jet is formed between the plates, and contaminant surface films that are detrimental to establishing a metallurgical bond are swept away in the jet. The metal plates, cleaned of surface films by the jet action, are joined at an internal point under influence of the very high pressure that is obtained near the collision point. Early patent issued in this area include U.S. Pat. Nos. 3,233,312, 3,397,444 and 3,493,353.
Each of the above known cladding methods requires the use of vacuum apparatus or other sophisticated equipment. In addition, the cladding method of the '504 patent, for example, is limited to the production of relatively thin gauge coil product and requires separately hot and cold rolling the substrate and cladding materials to sheet form before the cladding operation. With respect to explosive cladding, the process is typically expensive and labor-intensive, requires the use of dangerous explosive materials, and may result in a non-uniform, wavy interface between the substrate and cladding layers, which may be unsuitable for certain applications.
Accordingly, it would be advantageous to provide an alternative method for cladding stainless steels and other materials with alloy cladding materials. Such alternative method preferably does not require use of a vacuum furnace, explosive cladding equipment, or other sophisticated production equipment.